6x12 waterline tile

I’m deciding on pool tile. There are a lot of amazing stone look tiles that are 6”x13” that I love, we like modern not your typical glazed tile. Our builder isn’t too found of it because he says it looks more like a wall tile. Is there any functional reason to stay away from a 6x12” and do a typical 6”x6”? Our pool is a rectangle so no curves to contend with.

thanks,
Liz